rust-lang/rust · critical

`Copy`/`Clone` does not have an associated type: {:?}

Error message

`Copy`/`Clone` does not have an associated type: {:?}

What it means

A `panic!` in `consider_builtin_copy_clone_candidate`. The built-in `Copy` and `Clone` traits have no associated types; a `NormalizesTo` goal against them should never reach the copy/clone candidate. Like 307, this is a solver dispatch invariant — the candidate assembly must skip projection goals for marker traits.

Source

Thrown at compiler/rustc_next_trait_solver/src/solve/normalizes_to.rs:508

        _ecx: &mut EvalCtxt<'_, D>,
        goal: Goal<I, Self>,
    ) -> Result<Candidate<I>, NoSolutionOrRerunNonErased> {
        panic!("trait aliases do not have associated types: {:?}", goal);
    }

    fn consider_builtin_sizedness_candidates(
        _ecx: &mut EvalCtxt<'_, D>,
        goal: Goal<I, Self>,
        _sizedness: SizedTraitKind,
    ) -> Result<Candidate<I>, NoSolutionOrRerunNonErased> {
        panic!("`Sized`/`MetaSized` does not have an associated type: {:?}", goal);
    }

    fn consider_builtin_copy_clone_candidate(
        _ecx: &mut EvalCtxt<'_, D>,
        goal: Goal<I, Self>,
    ) -> Result<Candidate<I>, NoSolutionOrRerunNonErased> {
        panic!("`Copy`/`Clone` does not have an associated type: {:?}", goal);
    }

    fn consider_builtin_fn_ptr_trait_candidate(
        _ecx: &mut EvalCtxt<'_, D>,
        goal: Goal<I, Self>,
    ) -> Result<Candidate<I>, NoSolutionOrRerunNonErased> {
        panic!("`FnPtr` does not have an associated type: {:?}", goal);
    }

    fn consider_builtin_fn_trait_candidates(
        ecx: &mut EvalCtxt<'_, D>,
        goal: Goal<I, Self>,
        goal_kind: ty::ClosureKind,
    ) -> Result<Candidate<I>, NoSolutionOrRerunNonErased> {
        let cx = ecx.cx();
        let Some(tupled_inputs_and_output) =
            structural_traits::extract_tupled_inputs_and_output_from_callable(
                cx,

View on GitHub (pinned to 22057b88b0)

Solutions

1. Ensure no code path builds a projection whose trait is `Copy`/`Clone`.
2. If reached during normal compilation, reduce and file as a rustc ICE.
3. Work around by disabling `-Znext-solver`.

Example fix

// before — projecting on Copy (invalid)
fn f<T: Copy>() -> <T as Copy>::Out { todo!() }
// after — Copy has no associated type
fn f<T: Copy>() { todo!() }

// Copy / Clone also have no associated types.
fn is_copy_clone(tcx: TyCtxt<'_>, trait_def_id: DefId) -> bool {
    let copy  = tcx.lang_items().copy_trait();
    let clone = tcx.lang_items().clone_trait();
    copy == Some(trait_def_id) || clone == Some(trait_def_id)
}
if is_copy_clone(tcx, did) {
    return Err("Copy/Clone has no associated type");
}

fn projection_target_is_not_copy_clone(tcx: TyCtxt<'_>, did: DefId) -> bool {
    !is_copy_clone(tcx, did)
}

use std::panic;
match panic::catch_unwind(panic::AssertUnwindSafe(|| solver.normalizes_to(goal))) {
    Ok(v) => v,
    Err(_) => Err("do not project an associated type off Copy or Clone"),
}

When it happens

Trigger: A `NormalizesTo` goal whose trait is `Copy` or `Clone` is dispatched into the built-in copy/clone candidate assembly under the new solver.

Common situations: Code that synthesizes trait refs with `Copy`/`Clone` as the projection trait (e.g. proc-macro or compiler-internal IR); nightly regressions in candidate filtering.

Related errors

• `Sized`/`MetaSized` does not have an associated type: {:?}
• `FnPtr` does not have an associated type: {:?}
• reservation impl for trait with assoc item: {:?}
• trait aliases do not have associated types: {:?}
• `ConstKind::Param` should have been canonicalized to `Placeh

AI-assisted analysis of rust-lang/rust@22057b88b0 (2026-08-03). Data as JSON: /data/errors/36b625c8e302ecc5.json. Report an issue: GitHub.